From Quake Wiki
This suit will protect you against slime and water. You can't drown while wearing it, slime won't hurt you, and you can see a little better because it gives everything a tinge of green and makes the screen a little brighter. You don't necessarily want to grab the suit just because it's there, it won't do you a whole lot of good unless you actually need to use it for something (like staying underwater for a long period of time). It can't hurt, but don't go too far out of your way or risk being killed to get it. The biosuit also slows down lavaburn a little. You will still take damage, but the chances of being able to cross a small lava pool are increased.
|Items in Quake|
|Health | Ammo Boxes | Mega-Health | Quad Damage | Biosuit | Pentagram of Protection | Ring of Shadows | Green Armor | Yellow Armor | Red Armor|